Correlation between gelatinization percentage and viscosity of gelatinized rice flour using FIR source

Abstract

Rice flour based food processing industries pay more attention on the parameters which affect the final quality of the product. In this context gelatinization and viscosity are the two main quality parameters needed to be concerned more to increase the final product palatability and consumerbility. Gelatinization causes physical and chemical changes in the starch granule where water will be absorbed by the granules as a result of breaking hydrogen bonds in amylose and amylopectin. Far-infrared (FIR) is a heating technique, getting more popularized in food processing sector in worldwide because of its bounteous advantages. Research on gelatinization of rice flour by FIR is not reported elsewhere and is a new attempt. The polished rice (Oriza sativa indica) was grinded and sieved through 150µm sieve and gelatinized by using three ceramic coated FIR elements each having 650W by changing the combination of FIR intensity (17125.1, 14123.5 and 11254.3 W/m2 ) and FIR exposure time (1, 2, 3, 4, 6, 8, 9 and 10 seconds). FIR intensity was measured with a pyranometer. The degree of gelatinization percentage of rice flour was measured with the Iodomatric method as guidelines given by Wootton and Kensington (1989). Viscosity measurements were taken for 55% gelatinized starch solution using No 2 spindle, while shear rate was set up at 60 rpm throughout the experiment. The viscosity of gelatinized rice flour increases with gelatinization percentage linearly with a correlation coefficient (R2 ) of 0.9548. The increase of FIR intensity and exposure time with the gelatinization percentage, cause water absorption which results in viscosity incremental effect. There is a strong relationship between gelatinization percentage and viscosity; thus viscosity can be used as an alternative measurement for gelatinization.